Although I never read Tom Clancy’s “The Sum of All Fears” or saw the movie, that title has been rattling around my head for several scary weeks. By Friday, I could think of nothing else, so I dug into his plot.

In short, it features dramatic twists and turns and stereotypical bad guys and involves a near nuclear war between the United States and Russia.

Ho hum.

Oh, for the good old days of the Cold War, when evil was simply defined and neatly packaged. Now it comes in nonstop streaming, in all shapes and sizes, from near and far. The sum of our fears is larger than ever because there are so many terrifying parts.

Consider that New York had its first Ebola patient and a lone-wolf terror attack on the same day.

Those twin demons came just a day after emergency teams practiced responding to a pretend nuclear-bomb explosion in Times Square. In their scenario, 100,000 people died instantly, buildings were flattened for a half-mile in all directions and a radiation cloud hung over the city.

In ordinary times, those events would have been enough to scare the bejesus out of most people. But they were bracketed by more mayhem, including three terror attacks by Muslim converts.

Two were in Canada, the more sensational one forcing the prime minister to hide in a closet and a lockdown of Parliament. The attack in Queens left two NYPD officers injured, one seriously, by a homegrown American swinging a hatchet.

Only afterward did cops learn his Facebook postings were full of anti-American, anti-Christian and anti-Jewish rants and an appeal for jihad at home.

“America’s military is strong abroad, but they have never faced an internal mass revolt,” Zale Thompson wrote. “They are weaker at home. We are scattered and decentralized, we can use this as an advantage.”

All three murderous maniacs were killed, but not before pushing the anxiety meter ever higher. The chaos of the world is coming home.

Here’s the consolation — it’s not your imagination and you’re not alone.

A Politico poll finds most Americans a nervous wreck. Some 64 percent say the country is spinning out of control, while only 36 percent say the nation can meet its challenges.

The findings are reported as exclusive to each other, but I fit in both camps. Things are out of control, but they don’t have to be.

As Charles Krauthammer has said, decline is a choice. It can be reversed with public will and the right leadership.

We don’t have either now, which produces fear magnified by a sense of helplessness. It’s not just that the people in charge of keeping us safe aren’t up to the job. It’s that they are making things worse.

A travel ban from Ebola hot spots is a no-brainer, but Washington’s failure to impose one shows our leaders apparently have no brains. A belated quarantine requirement by Govs. Cuomo and Christie is a good start, but it came despite the feds’ dithering.

We chase after events, always surprised that feckless policies don’t work. The horse escaped the barn then, maybe, we’ll close the door.

Sometimes our bumbling bosses open the door in the first place. Mayor de Blasio made handcuffing cops a priority, and one of his first moves was to end surveillance of radical Muslims. The courts had upheld the program as constitutional, but that wasn’t good enough for Mr. Politically Correct.

If he hadn’t been so foolish, cops might have known that Thompson was looking to spill blood before he pulled out his hatchet. Instead, he was unknown to them until he struck.

How many others are still hidden because the NYPD cannot look for them? Does the mayor even care?

Even stout old Canada has succumbed to a fatal lack of will. The attack in Ottawa came just two days after a soldier was run over and killed near Montreal by a Canadian-born man who converted to Islam and became radicalized. He had tried to leave the country to fight with Islamic State, only to have his passport confiscated. Yet police say they didn’t have reason to arrest him.

Remarkably, the man who carried out the attack on Parliament was, profile-wise, a carbon copy. He was born in Canada, converted to Islam, tried to leave for the Mideast, had his passport confiscated and was considered dangerous, though not enough to arrest.

He started his assault with the coldblooded execution of a soldier at a war memorial. That soldier was “armed” with a ceremonial rifle that had no bullets.

So a doctor back from Africa is free to create chaos in New York, cops are injured by an Islamist who had declared his intentions, and a soldier protected by an empty gun is executed.

Those events aren’t just the sum of our fears. They are also the sum of our folly.

A sour note at the Met

Among the many great responses to my column on the fight at the opera, two stand out for their originality.

Reader Seymour Yusem refers to an op-ed in The Post by Peter Gelb, the general manager of The Metropolitan Opera and the person most responsible for staging “The Death of Klinghoffer.”

“It’s ironic that Gelb cites his experience with an attack by the Jewish Defense League. I don’t recall him making any attempt to ‘understand’ or ‘humanize’ the attackers of the JDL, or to commission an opera to that effect. He can’t have it both ways.”

And reader Robert Feinberg challenges the Met with an even larger historic event.

“Would the Met present an opera based on the ‘Death of Robert Kennedy Jr.’ by the Palestinian ‘freedom fighter’ Sirhan Sirhan? Why doesn’t the liberal establishment ever speak about Robert Kennedy’s assassination as a Palestinian terrorist act?”

Touché to both.

Whines of a ’90s vintage

In the same week that Monica Lewinsky declares herself a victim, her favorite president says he’s a victim, too. Sick of hearing how tough Barack Obama has it with Republicans, Hubba Bubba piped up to say that toxic partisanship was worse in his day.

“Nobody’s accused him of murder yet, as far as I know,” Clinton said in a TV interview. “I mean, it was pretty rough back then.”

His bellyaching is enough to make you tired of him all over again. Just imagine how much fun it will be reliving the past if you-know-who wins in 2016.

App-ropos of nothing

A new high-tech headband that connects to an app on your smartphone reportedly helps to regulate your breathing and calm you down.

Unless the connection doesn’t work, in which case you’ll go absolutely nuts and need a drink and a tranquilizer.